1. Field of the Invention
The present invention relates to an image forming apparatus, and in particular to a laser printer having a pre-exposing apparatus.
2. Description of the Related Art
In a conventional laser printer, an electronic photo process unit is formed by uniting parts of the electronic photo process components such as the photosensitive drum, the charging apparatus, a developing apparatus, a pre-exposing apparatus, and a cleaning apparatus, which are independently detachable from a main body of the printer. This is because, for example, the photosensitive drum becomes used up, and must be replaced. Moreover, the cleaning apparatus for cleaning the photosensitive drum is filled with toner within a fixed period of times and the entire cleaning apparatus must be replaced with a new one. These replacements must be performed by a user and the replacement method must be simple and free from errors.
Generally, in order to detect the presence of the detachable electronic photo process unit, which is mounted in the main body of the apparatus, a switch is provided in the main body side, or a charging output of the charging apparatus is detected.
However, if the presence of the electronic photo process unit is detected by the switch, the provision of the switch itself increases costs. Also, there is a problem in reliability of an actuator, which performs the ON/OFF operation of the switch, when the attaching and detaching operations of the unit are repeated. Moreover, if the presence of the electronic photo process unit is discriminated by detecting the charging output, an unfavorable influence is exerted on the photosensitive drum since charging must be performed when the unit is mounted on the main body.
In this type of laser printer, the specifications must be changed, depending on the customer of the OEM (original equipment manufacturing). Due to this, in a conventional apparatus, specific mechanism connecting sections in the main body of the apparatus, the process unit and the connecting section are modified for each customer (or each type of apparatus). However, if the shape of the connecting section is changed for each customer, manufacturing costs increase. Moreover, in a conventional apparatus, when a plurality of switches are provided in the apparatus and the unit is mounted thereon, binary data is generated, thereby the mount of the unit and the type are discriminated. In this case, additional I/O ports are needed, and manufacturing costs again increase.